Ships of the type with open stern walls are in common usage for transporting cargo lighters from one location to another. These ships are generally of a dual hull design that includes a system of ballast tanks that permit the ship to operate in a partially submerged or a fully floating mode. A first layer of lighters can be loaded on such ships by initially partially submerging the ship, floating the lighters into the cargo hold through the open stern wall, securing the lighters in place and then raising the ship to its floating position by evacuating the ballast tanks. The lighters are subsequently unloaded in the reverse manner when the ship reaches its destination. The lighters used in connection with such ships generally have a cargo carrying capacity of up to about 350 tons and a combined maximum weight including cargo of up to about 500 tons. Ships of this type typically carry about twenty or thirty lighters and are commonly used in inland waterways, but not generally used as ocean-going vessels.
Ocean-going transport systems have been provided wherein cargo is loaded in lighters which are floated to a ship. The lighters are lifted from the water and deposited in the cargo hold of the ship by a crane carried on the ship and subsequently unloaded in the reverse manner when the ship reaches its destination. The ocean-going cargo ships employed with such systems generally have a cargo handling capacity of about 90 to about 100 lighters and are of conventional hull design with entirely enclosed cargo holds and hatch covers for sealing such cargo holds. For example, U.S. Pat. No. 3,390,657 describes a gantry crane adapted for operation on a vessel to lift lighters and transport them from an outboard loading position astern the vessel to and through a hatch and into a cargo hold, the crane being located for travel on spaced rails extending longitudinally along opposite sides of the ship. The ship is disclosed as having spaced cantilevered stern beams which provide a platform on which the crane may travel to an outboard position for lifting a floating lighter from the water. The crane is used to lift the lighter out of the water vertically upward to a position above the cargo hatches of the ship and to transport the lighter to a particular cargo hatch and lower it into the cargo hold for storage. U.S. Pat. Nos. 3,469,716 and 3,515,086 describe a sea-going transport system that includes in combination with a gantry crane mounted on the deck of a ship a guide system for restraining swinging movement of lighters being transported from a floating position adjacent the stern of the ship to a storage position in the cargo hold of the ship. The guide system described in these patents includes a pair of lead-in stern guides pivotally depending from a pair of parallel spaced cantilevered stern beams which project horizontally from the stern of the ship, and a guide-rail-guide-carriage arrangement mounted on the legs of the gantry crane and adapted for restraining swinging movement U.S. Pat. No. 3,515,085 describes a load frame assembly for use with a sea-going transport system which includes a collapsible member for each ropefall of the hoisting system to maintain tension in the ropefalls when the lighter is tossed by sea swells. U.S. Pat. No. 3,536,204 describes an anchoring device for securing a traveling ship-board crane to the deck of the ship.
It would be advantageous to provide a system for transporting lighters from a floating position adjacent the stern of a ship to a storage location aboard said ship or for transporting such lighters from said storage location to said floating position that would be suitable for use with ships of the open stern wall type. Such a system would necessarily include guide members for restraining the swinging movement of the lighters when loading and unloading such lighters using the crane of the systems. However, such guide members would have to be designed in such a manner so as to also permit the loading and unloading of lighters by floating such lighters into or out of the cargo hold. It would be advantageous if such a system were of a simplified design and construction relative to the transport systems designed for use with conventional ocean-going cargo vessels.